Universal extractor for total endoprostheses (TEP) of the knee joint

Abstract

The invention relates to a universal extractor for total endoprostheses (TEP) of the knee joint. The object of the invention, namely to make available a universal extractor for artificial knee joints that avoids the disadvantages of the prior art, is achieved by the fact that the universal extractor comprises the following parts: a T-piece with an extraction plate and with a securing arm, the securing arm being fork-shaped and slotted at its distal end and supporting the extraction plate at its proximal end; a scissor mechanism with clamping jaws located at its free distal ends, said securing arm holding the scissor mechanism by means of a securing pin about which the scissor mechanism can move; and an eyebolt which is mounted on the proximal end of the scissor mechanism and has a knurled nut, the eyebolt being adjustable and connecting the ends of the scissor mechanism to each other, so as to permit fixing or release of the clamping jaws which have a shovel-shaped, U- to V-shaped geometry.

1. Universal extractor for a knee prosthesis, comprising
 a T-shaped element having a vertical member and a horizontal member affixed to a first end of the vertical member, the horizontal member comprising an extraction plate for receiving an extraction force upon extraction of the prosthesis and the vertical member comprising a securing arm, a second end portion of the vertical member defining a terminal end portion of the vertical member from which a pair of fork-shaped prongs and a prong bridging member extend so as to define a slot between the prongs, the prongs being symmetrical about an axis that passes therebetween and that is parallel with a longitudinal axis of each of the prongs and extending along their longitudinal dimension into a plane that is orthogonal to a plane in which the extraction plate extends in a longitudinal direction of the extraction plate; 
 a scissor mechanism comprising two intersecting arms, an intersecting portion of the arms being received in the slot so that each of the arms is free from direct contact with either of the prongs at a point directly adjacent the bridging member and the prongs, a first pin pivotably connecting the arms to the second end portion of the vertical member and to the prongs, and a respective clamping jaw carried on a distal end of each of the arms, the clamping jaws each being shovel-shaped or substantially U- or V-shaped or of a shape intermediate a U and a V, the point of connection of the arms to the second end portion defining a locus of force transfer between the arms, prongs and extraction plate upon extraction of a prosthesis so as to optimize an extraction force exerted upon the extraction plate during extraction of the prosthesis; and 
 an adjustment mechanism comprising an elongated member including an attached actuating portion, the adjustment mechanism adjustably connecting proximal ends of the arms so as to adjustably fix a distance between the proximal ends thereby to effect fixation and release of the jaws to and from a knee prosthesis, the arms being movable during a scissoring movement thereof through a plane that is orthogonal to the plane in which the longitudinal dimension of each of the prongs of the fork-shaped second end portion of the vertical member extends, and the actuating portion laying in a plane that is parallel to the plane through which scissoring movement of the arms occurs and orthogonal to the plane through which the longitudinal dimension of each of the prongs extends. 
 
     
     
       2. The universal extractor of  claim 1 , wherein the jaws are integral with the arms. 
     
     
       3. The universal extractor of  claim 1 , further comprising a respective aperture passing through each of the arms at the intersecting portion thereof to form a pair of axially aligned apertures through which the first pin passes. 
     
     
       4. The universal extractor of  claim 3 , further comprising at least one additional pair of apertures passing through the arms and through which the first pin is receivable, the apertures of each pair being spaced from other apertures in a length direction of the arms whereby changing the first pin from one of the pairs of the apertures to another of the pairs changes the location of the intersecting portions of the arms and also changes the clamping range of the jaws. 
     
     
       5. The universal extractor of  claim 1 , wherein the arms and the jaws are symmetrical about a plane through the T-shaped member thereby rendering the jaws self-centering.